Most of the underground mines in the world are developed through sinking of vertical shafts, because many naturally occurring mineral deposits are buried deep beneath the earth surface. Until recently, the most commonly used shaft development technique had been the method of conventional shaft sinking, which utilizes workers at the face of the shaft for manual drilling and blasting of rock, rock removal to the surface and installation of supporting shaft liner. The conveyance guiding and other facilities required in the shafts are also installed manually.
More recently, the method of full face shaft drilling had come to the fore, which is substantially more economical and safer than the conventional sinking. Unfortunately, for deeper deposits the diameter of drilled shafts is limited by difficulties in installing shaft liner or casing, and by other problems associated with drilling to the greater depths.
Most shafts must accommodate various mine services. These usually include at least two conveyances for hoisting of rock or mineral, with their guidance systems, electric cables, pipes for water supply or pumping, as well as other services. For that reason, the required diameters of shafts are quite large, which makes the shaft drilling method impractical for deeper mineral deposits.
An example of a mine shaft hoist and guide system is described in U.S. Pat. No. 4,601,607 to Lehmann, wherein a headframe supports a plurality of sheaves. The sheaves and associated cable and hoist move conveyances in and out of the shaft.
It would be therefore desirable to accommodate all the required services in the same or a greater number of smaller shafts. This would be easily possible, except for the hoisting facilities, because the typical hoisting system includes a single hoist with two conveyances, which have to be accommodated in a single shaft.